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test adding capture history #57

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kevlu8 merged 1 commit into from
Jun 22, 2025
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test adding capture history #57

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18 changes: 16 additions & 2 deletions engine/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,7 @@ Move killer[2][MAX_PLY];
* TODO: check if overflows are possible
*/
Value history[2][64][64];
Value capthist[6][6][64]; // [piece][captured piece][dst]

/**
* The counter-move heuristic is a move ordering heuristic that helps sort moves that
Expand All @@ -94,6 +95,11 @@ void update_history(bool side, Square from, Square to, Value bonus) {
history[side][from][to] += cbonus - history[side][from][to] * abs(bonus) / MAX_HISTORY;
}

void update_capthist(PieceType piece, PieceType captured, Square dst, Value bonus) {
int cbonus = std::clamp(bonus, (Value)(-MAX_HISTORY), MAX_HISTORY);
capthist[piece][captured][dst] += cbonus - capthist[piece][captured][dst] * abs(bonus) / MAX_HISTORY;
}

/**
* Perform the quiescence search
*
Expand Down Expand Up @@ -207,7 +213,8 @@ pzstd::vector<std::pair<Move, Value>> order_moves(Board &board, pzstd::vector<Mo
if (move == entry) continue; // Don't add the TT move again
Value score = 0;
if (board.piece_boards[OPPOCC(board.side)] & square_bits(move.dst())) {
score = MVV_LVA[board.mailbox[move.dst()] & 7][board.mailbox[move.src()] & 7];
// score = MVV_LVA[board.mailbox[move.dst()] & 7][board.mailbox[move.src()] & 7];
score = PieceValue[board.mailbox[move.dst()] & 7] + capthist[board.mailbox[move.src()] & 7][board.mailbox[move.dst()] & 7][move.dst()];
} else if (move.type() == PROMOTION) {
score = PieceValue[move.promotion() + KNIGHT] - PawnValue;
} else {
Expand Down Expand Up @@ -330,7 +337,7 @@ Value __recurse(Board &board, int depth, Value alpha = -VALUE_INFINITE, Value be

Move best_move = NullMove;

pzstd::vector<Move> quiets;
pzstd::vector<Move> quiets, captures;

for (int i = 0; i < moves.size(); i++) {
Move &move = scores[i].first;
Expand Down Expand Up @@ -406,6 +413,12 @@ Value __recurse(Board &board, int depth, Value alpha = -VALUE_INFINITE, Value be
update_history(board.side, qmove.src(), qmove.dst(), -bonus); // Penalize quiet moves
}
cmh[board.side][line[ply-1].src()][line[ply-1].dst()] = move; // Update counter-move history
} else {
const Value bonus = depth * depth;
update_capthist(PieceType(board.mailbox[move.src()] & 7), PieceType(board.mailbox[move.dst()] & 7), move.dst(), bonus);
for (auto &cmove : captures) {
update_capthist(PieceType(board.mailbox[cmove.src()] & 7), PieceType(board.mailbox[cmove.dst()] & 7), cmove.dst(), -bonus);
}
}
return best;
}
Expand All @@ -414,6 +427,7 @@ Value __recurse(Board &board, int depth, Value alpha = -VALUE_INFINITE, Value be
break;

if (!capt && !promo) quiets.push_back(move);
else if (capt) captures.push_back(move);
}

// Stalemate detection
Expand Down